Mixer blade assembly for medium and high viscosity liquid

Abstract

A mixer blade assembly is provided for medium and high viscosity liquid which does not cause the generation of an insufficiently mixed region of a doughnut-shaped configuration within the liquid to be mixed and therefore has excellent mixing performance. The mixer blade assembly for medium and high viscosity liquid includes a rotary shaft including at least two support posts spaced apart from each other; a plurality of plate-shaped inclined blades secured on each of the support posts and spaced apart from each other into multiple stages, the leading edge of each of the blades being displaced rearwardly or forwardly as viewed from the axis of blade rotation from the upper stage to the lower stage; and a bottom impeller secured on the support posts and being located in proximity with the bottom surface of the mixing vessel. The generation of an unmixed region of a doughnut-shaped configuration within the liquid can be eliminated due to generation of a one loop flow pattern within the mixing vessel, and an excellent mixing performance can be achieved for liquids with a wide range of Reynolds number due to suppression of the delamination of flow flowing over the upper surface of each blade.

What is claimed is: 
     
       1. A mixer blade assembly for medium and high viscosity liquids, comprising: a rotary shaft including at least two support posts spaced apart from each other and being positionable in a vessel, said shaft being positioned exclusively outside the vessel;   a plurality of plate-shaped inclined blades secured on each support post and spaced apart from each other so as to form multiple stages, each leading edge of said blades being displaced successively rearwardly or successively forwardly as at an angle of from 3-22° as viewed from an axis of blade rotation from an upper stage toward a lower stage so as to form a downwardly oblique liquid flow, said blades being exclusively positioned between said posts and an inner wall portion of said vessel; and   a bottom impeller secured on each of the support posts in proximity with a bottom surface portion of the mixing vessel so as to generate an upward liquid flow and promote mixing of the liquid, said two support posts being positioned in said vessel so as to form an unobstructed volume in the vessel between said support posts, said blades being displaced at said angle of advance to increase an area of each of the blades acting on the liquid and thereby cause a rectifying effect on the liquid in an upper stage of the blades and a dragging effect on the liquid in a lower stage of the blades to thereby improve mixing of the liquid.   
     
     
       2. A mixer blade assembly for medium and high viscosity liquid as claimed in claim 1 wherein a blade of the upper stage and a blade of the lower stage adjacent to the upper stage partially overlap each other as viewed in a vertical direction. 
     
     
       3. A mixer blade assembly for medium and high viscosity liquid as claimed in claim 1 wherein each blade is secured on one of the support posts so that an inner edge thereof intersects said one of said support posts at a predetermined angle and wherein an outer edge thereof contacts an inner surface of the mixing vessel. 
     
     
       4. A mixer blade assembly for medium and high viscosity liquid as claimed in claim 3 wherein an angle of inclination of the inclined blades is in a range of 18° through 48°. 
     
     
       5. A mixer blade assembly for medium and high viscosity liquid as claimed in claim 1 wherein said bottom impeller is secured on each of said support posts at opposite ends thereof; the side regions of the bottom impeller in proximity with the posts being vertically positioned so as to be swept back rearwardly as viewed from the axis blade rotation and a central region between the side regions has a height smaller than that of the side regions, and wherein the bottom edge of the impeller is positioned in proximity with the bottom surface of the mixing vessel. 
     
     
       6. A mixer blade assembly for medium and high viscosity liquid according to claim 1 wherein said plurality of blades form a new row of blades and at least the uppermost blades of the row of blades are positioned so as to project from the liquid during use. 
     
     
       7. A mixer blade assembly for medium and high viscosity liquid according to claim 1 wherein each of said blades comprise a plate having one of a flat, curved and a folded configuration. 
     
     
       8. A mixer blade assembly as claimed in claim 1, wherein said bottom impeller has a pair of side regions which connect, respectively, to the lower portion of the support posts and has a central portion of a reduced height to reduce resistance to flow of the liquids in a bottom portion of the vessel. 
     
     
       9. A mixer blade assembly as claimed in claim 1, wherein said blades are displaced successively forwardly from the upper stage to the lower stage as viewed from the axis of rotation. 
     
     
       10. A mixer blade assembly as claimed in claim 1, wherein said blades are displaced successively rearwardly from the upper stage to the lower stage as viewed from the axis of rotation. 
     
     
       11. A mixer blade assembly as claimed in claim 1, wherein a length dimension of successive blades from an upper stage to a lower stage are decreased. 
     
     
       12. A mixer blade assembly as claimed in claim 11, wherein trailing edges of said successive blades are in vertical alignment with one another. 
     
     
       13. A mixer blade assembly as claimed in claim 1, wherein trailing edges of said successive blades are in vertical alignment with one another. 
     
     
       14. A mixer blade assembly for medium and high viscosity liquids, comprising: a rotary shaft including at least two support posts spaced apart from each other and being positionable in a vessel, said shaft being positioned exclusively outside the vessel;   a plurality of plate-shaped inclined blades secured on each support post and spaced apart from each other so as to form multiple stages, each leading edge of said blades being displaced successively rearwardly or successively forwardly as at an angle of from 3-22° as viewed from an axis of blade rotation from an upper stage toward a lower stage so as to form a downwardly oblique liquid flow, said blades being exclusively positioned between said posts and an inner wall portion of said vessel; and   a bottom impeller secured on each of the support posts in proximity with a bottom surface portion of the mixing vessel so as to generate an upward liquid flow and promote mixing of the liquid, said blades being displaced at said angle of advance to increase an area of each of the blade acting on the liquid and to thereby cause a rectifying effect on the liquid in an upper stage of the blades and a dragging effect on the liquid in a lower stage of the blades to thereby improve mixing of the liquid, wherein a plurality of an auxiliary blades are mounted on the support posts radially inside thereof.